The positive impact of extreme heat on vegetation growth in Northeast Asia

The intensity and frequency of extreme climatic events have markedly increased in recent decades, leading to remarkable abnormal changes in terrestrial ecosystems. Understanding how vegetation growth responds to these climate extremes is crucial, yet inherently complex. We used two satellite-based vegetation indices to assess vegetation growth: the Normalised Difference Vegetation Index (NDVI) and Enhanced Vegetation Index (EVI). Event coincidence analysis (ECA) and sensitivity analysis were used to determine how extreme climates (extreme heat, cold, wet, and drought) have led to abnormal vegetation growth (vegetation high-growth and vegetation low-growth) over Northeast Asia, which exhibits unique biodiversity and increasingly confronts heightened climate vulnerability. Our results demonstrate that extreme heat promotes vegetation growth, whereas extreme cold adversely affects vegetation growth. Our study also identified a greater sensitivity of forest ecosystems to extreme heat than grasslands and shrublands, with croplands influenced by anthropogenic factors displaying the lowest sensitivity. The beneficial effect of extreme heat on vegetation growth weakens with increasing temperature gradients, but amplifies with rising humidity gradients. This indicated that extreme heat is beneficial for vegetation growth in cold and humid regions. This study identified the division of ecologically sensitive vegetation zones under climate extremes and emphasised the diverse impacts of climate extremes on vegetation growth in Northeast Asia. Our findings can serve as a significant scientific foundation for supporting society's efforts to mitigate and adapt to climate change.